Not knowing a lot about the internal politics of either Vietnam, I'd make an amateur guess that killing Ho Chi Minh wouldn't make much of a difference either way. The people in the North who were fighting/cheering for armed reunification with the South would likely continue in their previous posture. There might be a bit of a boost of morale in the South, but it wouldn't significantly alter the reality on the battlefield.
The biggest emotional impact might be in the USA where, if it's late in the war, the hawks will try to portray the death of Ho as some sort of major turning point in their direction, or at least that's what they'd tell the public. Still wouldn't do much to reverse the outcome.